In a car with an air bag for the front passenger seat, the passenger in the front passenger seat is protected by an air bag which operates when an unexpected collision occurs. In addition, there are provided various measures for preventing a diving phenomenon i.e. "submarine" phenomenon that occurs when an inertia at the collision causes the legs, especially knees, to hit directly and crumple the instrument panel, resulting in the passenger being pushed under the instrument panel.
FIG. 8 is a sectional view of a conventional instrument panel structure. FIG. 9 is an exploded perspective view of the instrument panel structure in FIG. 8. As shown in FIG. 8 and FIG. 9, an air bag 22 for the front seat passenger is mounted in an upper portion of a space within the instrument panel 21. A glove box 23 is arranged behind a lower portion of the instrument panel 21.
The glove box 23 is kept closed by a locking mechanism which engages with a striker 23B mounted at a bracket 23A. The bracket 23A is mounted on the inside of the instrument panel 21. A lid 23C covers the front surface of the glove box 23 i.e. the surface facing the front passenger seat.
A steering support beam 24 and a duct 25 for an air-conditioner are arranged within the instrument panel 21. The steering support beam 24 is laterally laid in front of the driver's seat and the front passenger seat. Both ends of the steering support beam 24 are connected to the front pillars (not shown) respectively to support the steering system on the side of the driver's seat.
Knee guards 26A and 26B are mounted on the steering support beam 24 on the front passenger seat side at positions to face the lid 23C of the glove box 23. A knee guard bar 27 is laid between the knee guards 26A and 26B. The knee guards 26A, 26B face the inside left edge and the inside right edge of the lid 23C respectively.
When an unexpected collision occurs, the knee guards 26A, 26B crumple to absorb the energy of the inertia F of the legs of the passenger in the front passenger seat and receive his knees and the lid 23C together with the steering support beam 24.
This prevents the glove box 23 and the front passenger from being pushed under the instrument panel 21, thereby preventing the so-called "submarine" phenomenon.
The knee guard bar 27 is a pipe element. The bar 27 is laterally laid between the knee guards 26A and 26B and the ends of the bar 27 are fixed to the knee guards 26A and 26B respectively. This serves to reinforce the mechanical strength of the knee guards 26A and 26B. During the collision, the bar 27 supports the instrument panel 21 on the reverse side, thereby preventing an excessive deformation of the instrumental panel 21, and also receive the chest thereby preventing the passenger from hitting his head against the windshield.
The duct 25 is communicated with any type of the air conditioners (not shown) to ventilate the outside air, inside circulated air, cooled air, heated air or the like into the interior of the car.
The duct 25 comprises a center duct ("duct center ventilation") 25A arranged in the central portion and a side duct ("duct side ventilation") 25B arranged on the passenger seat side. The duct center ventilation 25A is communicated with a central duct outlet ("grille center ventilation") 25C built into the middle of the instrument panel 21. The duct side ventilation 25B is connected with the duct center ventilation 25A and a side duct outlet ("grille side ventilation") 25D built into the passenger seat side of the instrument panel 21.
Some other techniques to prevent the "submarine" phenomenon are described in the Japanese Patent Laid-Open 234031/1985 and the Japanese Utility Model Laid-Open 46958/1992.
The above conventional instrument panel structures contain hollow ducts, the glove box (including brackets and a striker) and the air bag, which leaves a small remaining free space inside of the instrument panel structure, that is, within the dashboard. This makes it difficult to install other elements than the knee guards and the bar for preventing the submarine phenomenon.
In addition, the conventional "submarine" phenomenon prevention structure consists of a large number of elements. Furthermore each element must be strong, which causes to increase the complexity, manufacturing cost and the weight of the instrument panel structure.